See http://gcc.gnu.org/PR3106
Backported from gcc-3.0.x

Fixes error
  .../binutils-2.11.2/libiberty/strerror.c:468: error: conflicting types for `sys_nerr'
  /usr/include/stdio.h:258: error: previous declaration of `sys_nerr'
  make[1]: *** [strerror.o] Error 1
  make: *** [all-libiberty] Error 2
on Mac OS X.

--- gcc-2.95.3/libiberty/strerror.c.old	2004-03-24 16:23:19.000000000 -0800
+++ gcc-2.95.3/libiberty/strerror.c	2004-03-24 16:23:48.000000000 -0800
@@ -13,6 +13,7 @@
    incompatible with our later declaration, perhaps by using const
    attributes.  So we hide the declaration in errno.h (if any) using a
    macro. */
+#define sys_nerr sys_nerr__
 #define sys_errlist sys_errlist__
 #endif
 
@@ -20,6 +21,7 @@
 #include <errno.h>
 
 #ifdef HAVE_SYS_ERRLIST
+#undef sys_nerr
 #undef sys_errlist
 #endif